#!perl -w

use strict;

my %hash;
my $i = "A";
foreach ("A".."Z") {
        if ( (ord() - ord("A")) % 3 == 0) {
                $i++;
        }
        $hash{$_} = chr(ord($i) - 1);
}

foreach my $key (sort keys %hash) {
        print "$key => $hash{$key}\n";
}
__END__
A => A
B => A
C => A
D => B
E => B
F => B
G => C
H => C
I => C
J => D
K => D
L => D
M => E
N => E
O => E
P => F
Q => F
R => F
S => G
T => G
U => G
V => H
W => H
X => H
Y => I
Z => I